This invention relates to a system for connecting two intersecting wood members together in abutting relation, and more particularly relates to connectors, often referred to as nailing plates, made from sheet metal having a plurality of integral teeth struck therefrom for securing together two intersecting wood members of a wood structure.
Heretofore, the 2.times.4 studs of factory-made wall panel assemblies were secured to the 2.times.4 top and bottom plate members of the wall panel by means of nails driven through the plate members and endwise into the ends of the studs. While this nail connection between the studs and the plate members was relatively strong in shear, it was weak in both lateral bending and in tension.
In fabricating factory-made wall panels, rectangular nailing plates, such as shown in U.S. Pat. No. 3,841,194, have been used. These nailing plates were pressed or otherwise driven into the wood members at the intersections or joints of the wall panel by suitable and well-known apparatus. However, certain problems have been encountered. In order for a nailing plate connection to develop full strength, it is necessary that a certain minimum area of the nailing plate with a prescribed number of teeth therein be driven into each of the wood members to be connected together. Due to the arrangment of the 2.times.4 studs and the plate members of a wall panel structure, nailing plates the width of the stud members (i.e., about 11/2 inches) did not have a sufficient working area or number of teeth engaging the plate member to result in a strong joint and wall panels so fabricated were not sufficiently stiff to withstand the stresses of subsequent handling, transportation to building sites, and erection. On the other hand, if rectangular nailing plates were employed which were significantly wider than the studs (e.g., having a width of 3 inches or more) so as to ensure that a sufficient number of teeth engaged or were embedded in the plate member, a substantial portion of the area of these larger rectangular connectors did not engage the stud. Thus a number of teeth were not embedded in the wood members and these exposed teeth constituted a hazard not only to all those who had to handle the wall panel assemblies, but also were hazardous in subsequent construction work, such as during wiring where the insulation of electrical cables could be cut by the sharp tooth edges. Moreover the plate area from which the exposed teeth projected did not significantly increase the strength of the connection and the substantial increased costs of these larger connectors made their use for this purpose uneconomical.
This is an important commercial factor inasmuch as about 60% of the total cost of a nailing plate is the cost of the steel itself so that any significant area of the nailing plate where the teeth remain exposed represents excess and unwarranted cost. For example, to make a sound joint between a 2.times.4 stud and a 2.times.4 plate using two rectangular nailing plates, each engaging one exposed 3" length of stud (11/2" in width) and a 3" length of plate (11/2" wide) would require two 41/2".times.3" plates. Such plates would each have an area of 41/2 sq. in. of unembedded teeth or 9 sq. in. of the 27 sq. in. total area of the two opposed plates per joint which would not be effectively functioning. This unutilized one-third of the metal of the plates therefore represents excess cost. Furthermore, these areas of plates in which the teeth will not become embedded in the wood present another problem during the fabrication of the wood structures. Typically, plates are positioned above each junction of clamped abutting wood members by visually and manually aligning one edge thereof with the edge of the stud and another edge with the bottom edge of the wood plate, the rectangular nailing plate simply resting there with the tips of two-thirds of the teeth lightly resting on the wood surfaces. This would leave 41/2 sq. in. out of 131/2 sq. in. of nailing plate as an unsupported, unsymmetrical mass. As there is considerable vibration and movement involved in press positioning and operation at each joint to be formed, this unsupported mass increases the tendency for the nailing plates to shift and be dislocated from their visually aligned proper positions and this will result in unsatisfactory joints being formed.
Hence, there has been a long-standing need to develop a connector system for wall panels and other wood structures which overcomes the above-mentioned problems.
Reference may be made to U.S. Pat. No. 2,117,308 for a disclosure of a prior art connector in the same general field as the present invention.